DISEASES OF WILD PLANTS. 99 



veins, and concentrically zonate. The lines marking the zones are 

 slightly elevated and darker. 



Specimens collected: Georgetown, 2385; Von Ormy, 1162. 



PARTHENIUM. 



Rust (Puccinia xanthi S. var. ambrosiae B. and Rav.), — The sori, 

 produced on the lower surface of parthenium (Partheniiun hyster- 

 ophorus L.), are characteristically brown and aggregated in circular 

 patches. The spots show a yellowish-brown coloration on the upper 

 surface. 



Specimen collected: Kennedy, 2838. 



PEPPERGRASS. 



Downy mildew (Peronospora parasitica (P.) De By.). — This fungus 

 on the peppergrass (Lepidium virginicum L.) causes the under sur- 

 face of the leaves to appear downy white in small spots or extended 

 areas, while the upper surface of the diseased spots is pale yellow. 



Specimen collected : Austin, 2952. 



PIGWEED. 



Leaf -spot (Cercospora brackiata Ell. and Ev.). — The spots on the 

 pigweed (Amaranthus spp.) are first dark brown, becoming grayish 

 brown, subcircular or irregularly rounded, 3 to 5 mm. in diameter. 

 They become very abundant, causing the leaves to curl and dry. 



Specimen collected: On A. spinosus L. — Kennedy, 2827. 



White-rust (Albugo bliti (Biv.) Kuntze). — The formation of the 

 white pustules on the under surface of the leaves marks the presence 

 of this fungus. 



Specimens collected: (1) On A. alous L. — Austin, 376. (2) Oni. retroflexus 

 L.— Austin, 1315 ; San Marcos, 2092 ; Uvalde, 1935 ; Luling, 2229 ; Victoria, 2516 ; 

 Stockdale, 2635; San Antonio, 3179. (3) On A. spinosus L. — Llano, 1760; Lock- 

 hart, 2059; Falfurrias, 2448. 



POKE WEED. 



Leaf -spot (Cercospora fagellaris Ell. and Martin). — Circular or 

 slightly irregular brown spots 2 to 5 mm. in diameter appear on the 

 foliage of the pokeweed {Phytolacca americana L.). The spots have 

 a dark-brown, elevated border and they become grayish when older. 

 Frequently the}^ are abundantly formed on the leaf tips, resulting in 

 the drying of the affected portions. In some localities affected plants 

 were completely defoliated and dead. 



Specimens collected: Austin, 336; Brenham, 1458; New Braunfels, 1722: 

 Elgin, 1885; Bastrop. 2025; San Marcos, 2115; Cuero. 2603; Stockdale, 2622: 

 Gonzales, 2696 : Flatonia, 2744 ; Yoakum, 2769. 

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